This invention relates to a digital display device having one or more display patterns, which includes a pair of oppositely disposed electrodes and an electro-transmissive substance in the form of solid, liquid or liquid crystal. The device modifies a mode of the transmission of light when excited by an electric signal supplied to the electrodes. A typical example of the electro-transmissive display is a liquid crystal display, but this invention can also be applied to an electrochromatic display or the like.
With the pattern cognition in the human beings, the following is well known:
1. The reaction of the nerve network of the retina has, as shown in FIG. 1, maximum and minimum values at the adjacent portions to the boundary line between bright and dark portions, although there is no change in brightness at each portion to objective excitation. This is because the contour is accentuated by the excitation and mutual inhibition of the nerve system.
2. The same contrast phenomenon occurs in all systems in which the field contentionally existing the positive (irrigating) and negative (inhibitory) action exists.
In xerography, for example, the thick and solid region in black or grey color can not be copied very well. In xerography a selenium plate which has electrostatic charges loses the charges at the portions to which light beams are directed, so that charges are held in the dark portions. An amount of toner is then dusted on the selenium plate and is adsorbed at the portion having charges, then printed on a paper sheet and baked thereon. The electrostatic attractive force at a certain point is determined not only by the charges at that point but by the integrated effect of all of the adjacent electrostatic fields. The positive and negative pattern in the respective field resembles closely the pattern of the exciting and inhibitory components in the field of a nerve unit of the retina, resulting in the same phenomenon. Namely, the contour line is emphasized and the uniform region will disappear.
3. In FIG. 3 letters A and B are shown in which the regions surrounded by the contour lines are smeared away, but the letters can easily be recognized.
4. FIG. 4 shows two regions 2 and 3 separated by the contour line 1. Although the regions 2 and 3 are equal in brightness, the inner region 2 will seem brighter than the outer region 3.
5. In the art of reflection, the transmission of a certain pattern is frequently performed by sending the information relating to the contour of the pattern and the pattern reconstructing by using information relating to the amplitude between the maximum and minimum values at the contour. Similarly, in situations where pattern cognition is by human beings, the feature common to the patterns appears objectively different and is abstracted and sent to the cerebrum where the maximum and minimum values in the brightness in the nervous reaction is set. Accordingly, the visual effect of the contour effects the broader region adjacent to the local portion, as well as the local portion itself. The information relating to the visible brightness is set in accordance with the maximum and minimum values, and, as a result, the brightness at the adjacent regions is determined by the set value.
FIG. 5 illustrates a prior art liquid crystal display device which comprises an upper glass substrate 51, a transparent segment electrode 52, a layer of liquid crystal substance 53, a transparent common electrode 54, a lower glass substrate 55 and a reflecting plate 56.
The liquid crystal display device is manufactured by the well known process of vapor depositing indium oxide or the like on the whole surfaces of the substrate 51 and 55 to form a transparent electroconductive layer. The unnecessary portion of the layer is etched away and the remaining segment and common electrodes are left having the requisite pattern. By placing the substrates to as to face the electrode 52 with the electrode 54 with the layer of liquid crystal substance 53 disposed therebetween the requisite structure is assembled. When an alternating voltage is impressed across the electrodes, the optical status of the liquid crystal substance is altered so as to change the light transmitting condition.
With electrochromism display devices, the liquid crystal substance forming the layer 53 in FIG. 5 is replaced by an inorganic electrochromism display element and an insulating layer is provided between the electrochromism display element layer and the transparent common electrode 54.
FIG. 6 illustrates a pattern formed by transparent electrodes which comprises seven segments. As shown in this figure, the electrodes used in the prior art light transmission display device is constructed of a number of electro-conductive sections uniformly distributed over the whole segment region. Accordingly, each segment gives an even brightness by the optical transmitting effect when an alternating voltage is impressed across the electrodes facing one another. As has been stated, the visual cognition in human beings is accomplished by a mechanism in which the information relating to the contour line is obtained under the edge effect and then transmitted to the cerebrum where the information on the central part of the pattern is abstracted even if the brightness of the central part is not equal. Therefore, it can be said that the brightness of the central part may be lower than that of the contour part, if the central part has a sufficiently uniform brightness to be abstractable, because the pattern can be congnized as one having an even brightness.